1. Field of the Invention
The present invention relates to an instant photo film pack that is formed from plastic material and contains instant photo film units of peel-apart type.
2. Background Arts
As a self-developing instant photo film unit, a mono-sheet type and a peel-apart type are well-known. In U.S. Pat. No. 4,637,703 (corresponding to JP-B (Japanese Patent Publication No.) 5-62725) and JP-B No. 6-87155, the peel-apart type instant photo film unit is disclosed, wherein a photosensitive sheet and an image receiving sheet are contained in a pack case in a separated manner. Ten sheets of instant photo film units (hereinafter referred to as film unit) are stacked inside the pack case, to provide a instant photo film pack (hereinafter referred to as film pack) on the market.
The pack case is comprised of an case body, a bottom cover and a pressure plate. The case body is an upper component of the pack case, and has a box shape of a substantially rectangular. The case body has an exposure opening in a top wall, and a bottom opening in a bottom wall. The case body is formed from plastic by injection molding, and effectively shield ambient light at corners of the pack case. The bottom cover is a bottom component, and covers the bottom opening of the case body. The pressure plate is located between the case body and the bottom cover, and biased toward the upper surface of the case body by a spring member provided on the bottom cover, to press the photosensitive sheet against a top inner wall of the case body. The image receiving sheet is disposed below the pressure sheet. The photosensitive sheet and the image receiving sheet, contained respectively above and below the pressure plate, are connected with each other by a withdrawing sheet and a mask sheet. The bottom cover and the pressure plate are made of thin metal plates.
A bottom edge of a front wall of the case body is in such a position that its level is higher than the a bottom edges of a rear wall and lateral side walls. Thus, a passage opening for advancing the film unit outside is formed under the front wall when the bottom cover is coupled to the case body so as to cover the bottom opening.
The film pack is loaded in a pack holder which includes a pair of spread rollers and an ejection door. When the film pack is unused, the exposure opening is closed by a light-shielding sheet for shielding the photosensitive sheet from ambient light. When the film pack is loaded, one end of the light-shielding sheet is protruded from a tab exit slot formed through a top wall of the pack holder. The other end of the light-shielding sheet is fastened to the pressure plate together with the film units by staples by use of a stapler. When the protruding one distal end of the light-shielding sheet is manually pulled out, the other end thereof is torn away from the staple-fastened portion by means of a perforation line or notches, so the light-shielding sheet is drawn out through the tab exit slot. Thus, a first one of the photosensitive sheets is exposed through the exposure opening, and becomes ready for photography. One distal end of the light-shielding sheet is attached to one distal end of a tab. The other distal end of the tab is attached to the withdrawing sheet of the first film unit. When the light-shielding sheet is removed, the other distal end of the tab is protruded from the tab exit slot.
The tab is manually pulled out through the tab exit slot after exposure. Then, one end of the withdrawing sheet is moved to pass between the spread rollers, and is advanced out of the pack holder through the ejection door. Afterwards, the withdrawing sheet is manually pulled out, by which the photosensitive sheet comes to a position opposite to the image receiving sheet and pressed onto it by passing between the spread rollers. Concurrently, a developing solution pod, provided on the withdrawing sheet, is ruptured to spread developing solution between the photosensitive sheet and the image receiving sheet. After the film unit is completely pulled out of the spread rollers, a predetermined time for development and fixation is elapsed. Then, a positive image is appeared on the image receiving sheet, which is peeled away from the film unit to provide a photographic print.
When the image receiving sheet is moved while the tab is pulled out, deviation between the image receiving sheet and the photosensitive sheet is occurred. Then, a sponge pad is provided on the bottom cover. The sponge pad is held by folding a pair of tongue-shaped clip plates that are formed by making a cut into the bottom cover. While the tab is pulled out, the sponge pad comes in contact with the image receiving sheet, and the frictional force between the sponge pad and the image receiving sheet prevents the image receiving sheet from moving until the photosensitive sheet is overlapped completely with the image receiving sheet.
As set forth, the case body is formed from plastic material by injection molding, whereas the pressure plate and the bottom cover are made of thin metal plates. If one desires to abandon or recycle the film pack, it is needed to disassemble the film pack and classify the parts into same elements. In order to reduce the burden of classification, U.S. Pat. No. 6,192,197 discloses a film pack, in which the case body, bottom cover and the pressure plate are formed from plastic by injection molding.
However, in case of forming the bottom cover and the pressure plate from plastic material, since the bottom cover is poorer in strength than the conventional one made of metal plate, the developing solution pod is likely to be ruptured by external force prior to photography. Moreover, the bottom cover is likely to be off from the case body. In that case, the film unit is exposed to ambient light through the bottom opening. Thus, it is necessary to form the bottom cover thicker than the conventional one. In molding the bottom cover thicker without decreasing the internal size of the film pack, the film pack becomes larger than the conventional one, so it is impossible to load the film pack in the loading chamber. Moreover, in case of reducing the space for engaging the bottom cover with the case body, engagement between the case body and the bottom cover is weakened, which causes separation of the bottom cover.
On the other hand, it is necessary to provide a sponge pad for providing frictional force to the image receiving sheet. In case of forming the bottom cover from plastic material, which is hard to bend to form clip plates like the conventional bottom plate, it is difficult to hold the sponge pad tightly. Moreover, separation of the sponge pad is required for classification after use the film pack. When the sponge pad is tightly stuck to the bottom plate by use of an adhesive or the like, refuse of the sponge is remained on the bottom lid after peeling off the sponge pad. In that case, it is difficult to make an effective classification of the film pack.
In view of the foregoing, an object of the present invention is to provide an instant photo film pack for preventing rupture of the developing solution pod and separation of the plastic-formed bottom cover by increasing strength without enlarging the pack size.
Another object of the present invention is to provide an instant photo film pack for securing an removably attachable sponge pad to the bottom cover formed from plastic material.
To achieve the above objects, an instant photo film pack of the present invention is comprised of a box-shaped case body, a pressure plate and a bottom cover which are formed from plastic material, and a pair of ribs provided on the bottom of lateral walls of the case body. The case body has a top wall with an exposure opening for allowing exposure to a photosensitive sheet. The pressure plate is located inside the case body between a plurality of stacked photosensitive sheets and a plurality of stacked image receiving sheets, and presses the photosensitive sheets toward said exposure opening. The bottom cover includes a bottom plate for covering bottom side of the case body, lateral walls stretched upward from the bottom plate, and engaging ridges integrated with the lateral walls and projected toward inside of the bottom cover. Bottom surfaces of the engaging ridges have inclined planes that increases the height of the engaging ridges gradually toward edges thereof, and top surfaces of the ribs is inclined so as to fit the inclined planes. Thus, ribs are fit into engaging grooves formed in spaces surrounded by the bottom plate, the lateral walls and the engaging ridges, so the bottom cover is firmly coupled to the case body without being away from the case body by external force.
The lateral walls of the case body is inclined to narrow the width of the case body gradually toward the top wall. Inclination of the lateral wall in an upper portion is larger than that in a lower portion. Thereby, it is possible to increase the area where the top surface of the ribs and the bottom surface of the engaging ridges are contacted to each other, so the strength of the engagement between the case body and the bottom cover is increased without increasing the size of the film pack.
By sliding the bottom cover after insertion of the ribs into the engaging grooves, a pair of engaging projections provided on the bottom cover is fit into engaging recesses provided in the ribs, and rear walls of the case body and the bottom cover are contacted to each other. So it is possible to fix the bottom cover at a predetermined position of the case body.
In order to prevent rupture of the processing solution pod, the bottom plate has a pair of pod protection ridges on both inner lateral sides of an area on which a developing solution pod of the instant photo film unit is positioned. Moreover, the bottom cover has a plurality of pod protection projections on inner corner of the bottom rear wall and the bottom plate, and mark for indication prohibition of depression on an area of outer wall where the developing solution pod is positioned.
In the embodiment, a sponge sheet is attached to a leading portion of the bottom cover for preventing image receiving sheets from moving by frictional force. The sponge sheet has two holes arranged in the direction perpendicular to the withdrawing direction of the instant photo film unit. Two projections are integrated with the bottom cover for inserting into the holes. After insertion, the projections are subjected to pressure and heat, so that the projections are deformed to cut into the sponge sheet. Thus, it is possible to attach the sponge sheet firmly on the bottom cover without having refuse in disassembling the film pack.